Another significant carrier consideration is that VCC builds on an IMS core they may not have. Analysts have reported significant progress with IMS deployments, usually focused around specific applications, so this concern will erode over time; Sprint, Cingular, FT, Telefonica and Softbank Mobile have all rolled out IMS infrastructures.
Designed primarily for voice, VCC also lacks true data, multimedia and video support, including basic cellular telephony services such as SMS and MMS, while UMA supports the last two items and GPRS. Considering that, according to Forrester, wireless carriers are reporting that the data component of ARPU ranges from 12 percent to 16 percent, this feature gap cannot be ignored. The Internet still can be accessed over the Wi-Fi and cellular data (2.5/3G) links, but the data session continuity will be lost as the handset roams because data sessions are not tunneled through the CCCF.
There is also a question around the role of VCC once cellular networks support end-to-end IP. Third-party vendors have stated that EV-DO Rev. A provides the necessary bandwidth and low latency to support native IP voice services from the handset to the cellular core, and future advances will likely continue along this line. If it becomes "all IP" the requirement for an anchoring CCCF falls away.
Supplementary services, such as call hold, call waiting and call forwarding, aren't available or are handled differently by various operators. End-users expect feature consistency no matter the access network they happen to be on.
